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3 x 15 + 21 x 15 + 85 x 5
= 45 + 315 + 425
= 785
15 - 30 + 40
= 25
21 + 19 - 50 + 10
= 0
\(\dfrac{1}{5}-\dfrac{1}{4}+2\)
\(=-\dfrac{1}{20}+2\)
\(=\dfrac{39}{20}\)
\(\left(\dfrac{1}{4}+\dfrac{1}{6}\right)\times\left(\dfrac{1}{2}-\dfrac{1}{4}\right)\)
\(=\dfrac{5}{12}\times\dfrac{1}{4}\)
\(=\dfrac{5}{12}\times\dfrac{3}{12}\)
\(=\dfrac{5}{48}\)
\(\dfrac{1}{10}+\dfrac{1}{5}-\dfrac{3}{4}\)
\(=-\dfrac{9}{20}\)
\(3\times15+21\times15+85\times5\\ =15\times\left(3+21\right)+425\\ =15\times24+425\\ =360+425\\ =785\)
\(15-30+40\\ =\left(15+40\right)-30\\ =55-30\\ =25\)
\(21+19-50+10\\ =\left(21+19\right)-\left(50-10\right)\\ =40-40\\ =0\)
\(\dfrac{1}{5}-\dfrac{1}{4}+2\)
\(=\dfrac{4}{20}-\dfrac{5}{20}+\dfrac{40}{20}\)
\(=\dfrac{\left(4+40\right)}{20}-\dfrac{5}{20}\)
\(=\dfrac{44}{20}-\dfrac{5}{20}\)
\(=\dfrac{39}{20}\)
\(\left(\dfrac{1}{4}+\dfrac{1}{6}\right)\times\left(\dfrac{1}{2}-\dfrac{1}{4}\right)\)
\(=\dfrac{5}{12}\times\dfrac{1}{4}\)
\(=\dfrac{5}{48}\)
\(\dfrac{1}{10}+\dfrac{1}{5}-\dfrac{3}{4}\)
\(=\dfrac{2}{20}+\dfrac{4}{20}-\dfrac{15}{20}\)
\(=\dfrac{6}{20}-\dfrac{15}{20}\)
\(=-\dfrac{9}{20}\)
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\(\frac{7}{3}+\frac{13}{3}=\frac{7+13}{3}=\frac{20}{3}\)
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`#3107.101107`
a)
\(x\times\dfrac{4}{5}\div2=\dfrac{6}{7}\\x\times\dfrac{2}{5}=\dfrac{6}{7}\\ x=\dfrac{6}{7}\div\dfrac{2}{5}\\ x=\dfrac{15}{7} \)
Vậy, \(x=\dfrac{15}{7}\)
b)
\(\dfrac{6}{5}\div x\div\dfrac{5}{4}=\dfrac{10}{15}\\ \dfrac{24}{25}\div x=\dfrac{10}{15}\\ x=\dfrac{24}{15}\div\dfrac{10}{15}\\ x=\dfrac{36}{25}\)
Vậy, \(x=\dfrac{36}{25}.\)
![](https://rs.olm.vn/images/avt/0.png?1311)
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a: =>7/9:x=1/18-2/9=1/18-4/18=-3/18=-1/6
=>x=-7/9:1/6=-7/9*6=-42/9=-14/3
b: =>x*7/5=2/15+2/5=8/15
=>x=8/15:7/5=8/21
c: =>x-1/2=3/14:4/7=3/8
=>x=3/8+4/8=7/8
d: =>0,4x+0,3x-0,2x=0,7
=>0,5x=0,7
=>x=1,4
![](https://rs.olm.vn/images/avt/0.png?1311)
x*4/5:2=6/7
x*4/5=6/7*2
x*4/5=12/7
x=12/7:4/5
x=15/7
6/5:x:5/4=10/15
6/5:x=10/15*5/4
6/5:x=5/6
x=6/5:5/6
x=36/25
bằng 2,5
ai k mk mk k lại cho nha
( 5 + 5 + 5 + 5 ) : 4 - ( 10 + 10 - 15 ) : 2
= 20 : 4 - 5 : 2
= 5 - 2,5
= 2,5
Đáp số : 2,5